No clearance lights

[Yakherder]

Last fall on my way home from Wyoming I had the clearance light fail to come on. I checked the fuses in the truck and found that the 30A in the box under the hood had blown. Changed it and blew again. I seemed to recall having this problem once before and that there was also a fuse under the dash that had blown as well. Took it in to the Toyota dealer in Sioux Falls and told him the problem and that there was a fuse under the dash that probably needed to be replaced. Came back two hours later and he said that they had indeed replaced the fuse. Just as I was leaving I wanted to reconfirm the fuse. He said the 30A under the hood and didn't look under the dash.

Well drove home in daylight and it has sat for the winter. I plan on taking a gander at this soon and was wondering if I could get the short version if someone else has had the same problem.

The clearance light run on the green wire from the truck to the trailer and are connected together in the junction box on the tongue frame.

It turns out my green wire is connected to a 20A Auto Reset breaker inside the junction box which is taped up to protect the contacts from touching any of the metal parts. I am not sure it this is needed????? or should it just be wired green to green.

It would appear to be a short somewhere but where. Power is good from the tow vehicle so it is somewhere back to the last clearance light I guess.

Where is the best place to start and is there a common location that a short will occur? How do you test for a short in the fixture?

And while I have everyone's attention, has anyone changed over the metal junction box on the tongue to a water proof box and if so where did you get a decent one?

Thanks for any help you can provide. Stay safe out there.

[DavisK]

In late 2018 my trailer was blowing the truck's fuse for the wire that goes to the right brake/turn signal. After some diagnosis I found that the heavy connecting cable that runs from the pin box to the truck's connector was pinched and had a short between the ground and the right brake/turn signal. I temporarily spliced the frayed wires and eventually replaced the connecting cable.

[Yakherder]

Thanks DavisK for the post.

I checked out the wires from the junction box out to the tow vehicle and all have continuity. I erred in my earlier post in stating that it was the green wire that controlled the running lights. It is the brown wire from the cable to the brown/white wire which runs through the trailer that connects to the tail lights and clearance lights along the sides and top at the rear of the trailer.

I ran separate power from the battery to the brown/white wire only, which should have turned on the tail and clearance lights. Only the passenger side tail light came on all the rest are out.

The question is, where do I begin to find where the short is. Do I pull off each clearance light/tail light and check the wiring or is there a simpler way of doing it. I would hate to have to open up the bottom of the trailer or god forbid the walls.

[woodwalker]

You may have a splice or connector loose from the front of the trailer to the back. Only way to find out id to drop the belly and trace the wire. I would ad yo said check th e connector at the tail lights before going to the other trouble

[Yakherder]

Thanks woodwalker for the info.

Seeing that I have one tail light that works, I can assume that the power is going from the front to the back before it splits off to the other lights.

It would be great to have a wiring diagram for my trailer but from reading other posts on electrical that is virtually impossible as they don't seem to wire every one the same way.

I guess I should pop the tail lights off to start and go from the one that has power to the driver side tail light and see if there is continuity with power and ground wires. I'm just guessing on this approach.

I have heard of OHM readings but have no idea how to do it and what I'm looking for in a reading. Continuity should tell me something. Don't want to have to take the belly off after replacing 80% of it last summer.

[mark5w]

I'd start with the taillights like you stated. It's the easiest to do before you take on the job of dropping the belly cover.

[Yakherder]

Thanks Mark5W. Sounds like the best place to start.

What would you recommend - Continuity or OHM's or Power at each of the terminals on the lights.

[mark5w]

Check for power at light. Trace wire and check for continuity.

[Yakherder]

Worked on the lights today. Popped off passenger side tail light and two clearance lights to check the color wires. The tail light has green and brown running to it and the clearance lights have just the green. (both have the white ground also).

Also installed new light bulbs just to make sure none were burnt out.

Isolated the brown and Green wires at the junction box and ran power direct. With the brown connected to 12v just the passenger side tail light came on. Hooked up to the green and all clearance lights came on and both tail lights.

It would appear that the problem is in the brown wire connecting to the driver's side tail light.

I am going to pop off the other tail light and check the wiring at that point tomorrow. Will check the power and continuity until I find the problem.
I should mention that when I opened up one of the clearance lights the wires were jammed into this little hole and the wires bent pretty bad. Adding to this CR ran the wires through one of the metal supports leaving a couple of jagged pieces of aluminum where they butchered the hole. The outside of the wires were scuffed but did not appear to be cut. Have to fix that up too.

Having a problem getting the right wiring diagram for a 7 pin connector. I have three versions and the colors are in a different order. I'll just have to make my own color code working from the truck back. On the truck it is a plug and play by Toyota so they must know what they are doing. All my lights worked before so there shouldn't be a problem with the way the trailer plug is hooked up.

Lots of time to work on this as we don't plan on going too far this year with the trailer.

[DavisK]

This is the color scheme used on both my truck and my camper.

[Yakherder]

Sorry DavisK but my color wires do not match yours.

But, I got the problem fixed.

Took every ones advice and did some research on wiring and found that there are different systems out there so I figured I should just make my own schematic of the wires that I have.

As mentioned before, my truck wiring was plug and play with the connector. The trailer has the original cord and wiring. Both worked great for the past three years so figured it has to be a short.

Checked all the wiring at truck for power and which wire operated what. I checked it again at the junction box on the trailer for the same. Everything working so far.

Unhooked all the wires in the junction box and ran a jumper wire from the battery and checked each one individually until I found which component did not work. Turns out it was the green wire which controls the tail and running lights.

Popped off the two tail lights and wiring appeared to be ok. Removed two clearance lights and found the problem behind one of the lights. The wire was crimped and shorting out.

Spliced in some extra wire and replaced the wire connectors to the light and rechecked the lights.

All working as they should.

Thanks everyone for the help.

[Keithdodge2001]

Same issue with 2008 ram and I tried a lot of things. After 2 weeks of searching I said forget this and completely rewired the trailer plug and the entire trailer for all the lights

[Yakherder]

KiethDodge2001, sounds like that was a mega job to complete.

All I had to do was fix the broken wire. To find it was a bit frustrating when not really sure which wire connected to what. I guess sorting out the wires at the truck and trailer harness then in the junction box lets you know what powers what wire. Then it is to check the lights, as in my case, and go from there. The wiring in my latest repair had been run through the metal support upright at the corner of the trailer. This support is part of the side wall frame and was only being held by one side of the post. The rest had been drilled/cut off in a butcher job to run the wire up from the rear tail light and out the side of the trailer for the marker light. Sharp jagged pieces were still in the opening that rubbed on the wires.

If I couldn't have found the short in any of the lights then I may have had to go the route you took and rewire all the lights.

The wiring in my trailer is something to behold. When I had to replace my underbelly last year I found a mess of wires. Once the belly was taken off they all fell out on the ground. None were secured to the frame to keep them from rubbing. Found some that were broken and had to be repaired. Poor workmanship.

[Keithdodge2001]

Yes it was a job and a half lucky for me I wire railroad crossings for a living and was able to take 3 days off for vacation to do it all. Some times it is easier to cut out everything and start from scratch. Kind of gives me a warm fuzzy feeling knowing that all is new the 5 the wheel was a mess. But now I have a print/schematic for everything